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WAN - Network Design & Planning Process

Concept & Introduction

companyInteractive Euro Technologies (IET) has a group of experts & professionals who specialize in the execution of enterprise & security networks and have the ability to respond to the most demanding challenges. The greatest asset of IET is our experienced personnel available on board. With experiences across multiple technologies and across regions, IET is positioned to provide the right people in the right place at the right time. Additionally, IET is committed to the technical and the professional development of our engineers making IET a smart decision for engineers as well as our customers

Network owners engage professionals to plan & design Wide Area Networks, Global System Mobile (GSM) & Code Division Multiple Access (CDMA) Networks and other services for a variety of reasons. One is network performance. IET guarantees by providing survey, planning, optimization, management, training and technical know-how. Another is financial predictability. IET offers fixed price long-term contracts – a clear advantage that gives the network owner a predictable and stable cost profile over the years. Outsourcing to IET means that we take care of everything from survey, RF planning, evaluation, system designing, transmission planning, test drive, optimization, training and management of the O&M staff, to network performance & availability, 24-hours network monitoring, technical support and maintenance.

Microwave Network Design Process

A. Determine design objectives

Main objectives of the transmission network are to satisfy capacity demands and provide reliable service.

  • Availability target for network.
  • Availability target for radio path.
  • Required capacity (current and future, i.e. as far out as the fourth year or beyond).
  • Maintainability, i.e. protected or non-protected. Protection schemes could be frequency diversity, space diversity, and monitored hot-standby (MHSB).
    • Both space and frequency diversity provides protection against path fading due to multi-path propagation in addition to providing protection against equipment failure. Such techniques are typically required in bands below 10GHz, specifically for long paths over flat terrain or over areas subject to atmospheric inversion layers.
    • Space diversity requires use of additional antennas, which must be separated vertically in line with engineering calculations.
    • Frequency diversity can be achieved with one antenna per terminal configured with a dual-pole feed. Its disadvantage is requiring two frequency channels per link, which is frequency inefficient.
    • MHSB protection can be used at frequencies below 10GHz if the path conditions are suitable. It is also the normal protection scheme at higher frequencies where multi-path fading is of negligible concern. It uses one single-feed antenna per terminal, utilizing only one frequency channel per link.
    • The transmission section of the network is a critical component of any network and care must be taken to plan accordingly.
  • Determine optimum packaging style for easy installation and proper fit: i.e., outdoor cabinets or equipment shelters. Mounting the RF unit outdoors allows the system to be designed with minimum use of wave-guide, which saves on costs, reduces losses, and reduces efforts in installation and commissioning.
  • All routes must be sized to meet service demands
  • Traffic must be routed in the most economical manner.
  • Survivability must be built into the network

B. Determine and produce (preliminary) network design

A preliminary network design is required to establish all of the nodes within the network, which requires transmission links between them. This can then be developed to become the main reference document for network planning and implementation.

It is critical that a transmission plan is established indicating current and potential future cell sites.

  • To accommodate this expansion, transmission backbone originating from the switch locations must be present.
  • The microwave hub sites making up the backbone's nodes must also be capable of simplifying growth.
  • The tower design, equipment shelter space, power and antenna type (dual-feed and/or high performance) should all be chosen with an eye towards expansion.
  • Microwave spur links, which terminate at the hub sites to connect those sites not located on the backbone, should be considered with a high capacity to accommodate traffic requirements.
  • As part of the initial plan, a transmission network diagram with standard symbols should be established and meticulously maintained as the network evolves. Also in consideration are: protection systems, star networks, transmission loops, diverse routing, microwave path availability, and network management systems.
  • Protection system – well designed, high capacity backbone and hub sites have Monitor Hot Standby (MHSB) radio to improve network reliability and reduce downtime.
  • If unprotected radios must be used, they should be deployed only to serve single end sites.

It is critical that a transmission plan is established indicating current and potential future cell sites.

It is critical that a transmission plan is established indicating current and potential future cell sites.

B.1. Star Network

Contains one or more hub sites at strategic locations, which serve spurs or chains of sub-ordinate sites from centralized hub. It can be multi-layered in that some of the nodes in a spur may be hub sites for further subordinate spurs. Protecting some or all of the links is a must, especially the hubs on the backbone. If a transmission link serves more than one dependent site, it is worthwhile considering protecting that link. Likewise, if a particular site is likely to be located in an area that is difficult to access, a protected system will ensure the integrity of the traffic to and from that site – this decision may, however, have to wait until the site selection process is underway. The hub sites should usually be limited to serving a maximum of six or seven cell sites to maintain good network reliability.

Disadvantage: Outages on a single transmission link may affect many sites and have a significant effect on overall network availability.

B.2. Ring Network

Contains one or more hub sites at strategic locations, which serve spurs or chains of sub-ordinate sites from centralized hub. It can be multi-layered in that some of the nodes in a spur may be hub sites for further subordinate spurs. Protecting some or all of the links is a must, especially the hubs on the backbone. If a transmission link serves more than one dependent site, it is worthwhile considering protecting that link. Likewise, if a particular site is likely to be located in an area that is difficult to access, a protected system will ensure the integrity of the traffic to and from that site – this decision may, however, have to wait until the site selection process is underway. The hub sites should usually be limited to serving a maximum of six or seven cell sites to maintain good network reliability.

Advantage: The rings can be used to provide path diversity and integrity to the network, and can remove the need for duplication (i.e. protection) of single links.

B.3. Hybrid ring / star networks

It is common practice for a combination of both, with the eventual choice of topology largely based upon economics and operational targets.

The network diagram can help highlight critical points of vulnerability in the network. Due consideration can then be given to the consequences of losing whole sites in the network in the event of a disaster. Likewise, the network diagram can be used to indicate critical paths within the network. Once a network diagram is established, it can help to evaluate consequences of future network growth and forecasts for the future can be superimposed accordingly. It is important to look at the consequences of growth both in terms of capacity and number of links.

Transmission loops in a network infrastructure provide diverse routing, so increasing the transport system reliability. As network's number of cell sites grows, a system of transmission loops should be established between major hub sites and switches to increase survivability and reliability. The backbone system can be upgraded to a higher speed and capacity system.

Diverse routing is recommended for transmission links between major hub sites and switches. One option is to keep available a redundant route with the capacity to carry all the traffic in case the main route fails; another is to use the diverse route at all times so that traffic is spilt 50/50.

C. Determine local frequency availability and regulatory restrictions relating to frequency management and microwave path availabilities.

It is common practice for a combination of both, with the eventual choice of topology largely based upon economics and operational targets.

An operator must determine available frequency bands and channel plans specific to that country. Most regulatory authorities also operate a local link length policy, where the particular path will determine what frequency bands are available for the operator to choose from.

Type approval is generally the responsibility of the radio supplier, but an operator should ensure that all requirements are satisfied before links are deployed. Other limitations imposed by authorities are tower restrictions, limitation upon antenna size, etc. These factors can restrict effective radio lengths at the planning stage and should be ascertained in advance of the detailed link design stage.

C.1. Digital Microwave Radio

Products are commonly available at interface rates from 2Mbps through multiples of 155Mbps, with interfaces designed to ITU-T standards. Additionally, products are also designed to meet international standards concerning frequency planning, which are published by the ITU-R.

C.2. Frequency Bands

The ITU-R organization defines a number of specific frequency bands, which are allocated on a primary basis to the fixed service – i.e. for microwave and millimetric point-to-point links.

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As a general rule, the higher the frequencies band, the shorter the usable distance of the link. In extreme case, use of frequency bands above 20GHz in tropical areas will limit path length to just a few kilometers. As a result, most efficient use of the frequency spectrum can be made by using lower frequency bands for longer paths, and higher frequencies for shorter paths.

C.3. Frequency Management

It is essential to determine, at the earliest opportunity, what bands are locally available for microwave fixed link systems, and what the local 'link length policy' is. Both these factors have a fundamental effect on the network plan.

Microwave path availability is the starting point of any microwave system design and is based on one microwave link. Since digital signals require full duplex operation, this availability should be based on a two-way capability.

Path availability targets should also be established and the operator should calculate its target availability, taking into account overall network availability required and network integrity as a function of the topology chosen. Preliminary path budgets are normally calculated either in the form of a spreadsheet, or using software tools available from equipment manufacturers.

Path availability of a specific microwave link is a factor of a number of components in relation to the path budget, which will take into account net output power expressed as an equivalent isotropic radiated power (EIRP) figure at the antenna, free-space attenuation in the frequency band in question, and receiver sensitivity. It is essential to establish whether local frequency management authorities will support customer's objectives.

A recommended alternative approach is to lobby the local frequency management authorities for exclusive allocation of a number of channels in applicable fixed link frequency bands, which can be planned and managed by the operator. It is fundamental that future network growth is considered, as planning links with unnecessarily high EIRPs can lead to congestion problems in the future.

A network management system is essential in a transmission network. A centralized automatic control system using computer technology provides operating and maintenance personnel with real-time direct access to the network's functional entities.

D. Select and survey sites

There are economical and engineering benefits to be gained by maximizing the sharing of infrastructure and sites between the various types of elements in the network, particularly regarding expensive civil infrastructure such as towers and equipment housings. Furthermore, minimizing the number of required sites in customer's network will bring logistical benefits, and control real estate investments or site leasing costs.

Therefore, it is always critical when selecting sites that no specific network element is considered in isolation. A number of specific items to bear in mind are:

  • Good microwave sites, particularly in relation to hub sites, will be relatively high points to provide the maximum line-of site availability. If a site is unsuitable, alternative sites should be located. This information should be fed back into the network plan as it can affect both routing and path planning.
  • If at all possible, share any towers or poles required between the wireless and cellular equipment and microwave fixed link outdoor equipment. Likewise, indoor equipment can be housed in the same equipment shelters and should be planned accordingly. Power requirements can be planned on this basis.
  • Required loading needs to be calculated if new installations are proposed, and these must take into account the antenna wind and ice loading. New terminals being added to an existing tower require calculations that ensure incremental loading can be accommodated.
  • When considering cable routing, bear in mind the separation distances between the indoor unit and RF unit in addition to the distance between the RF unit and antenna. Additionally, distances between the indoor unit and any other co-located network element should be evaluated. Cable and/or wave-guide routing should be checked, including length and securing, building a network interconnecting the WLL network and switching elements.
  • An operator should aim to perform only one site survey to minimize costs. Equipment installation requirements must be confirmed – power, accommodation, and environmental. If a site is in a rural or remote area, the service access should always be considered, particularly in times of inclement weather. Attention should be given to access to tower mounted elements, both in relation to the weather and to the experience and qualifications of the maintenance staff.
  • Attention should be given to future growth requirements in all areas, especially if the site is likely to develop into a future hub. It is good practice to inform landowners of any potential future growth to prevent problems at a later date
  • Attention should be paid to any local authority planning restrictions and approvals for structures or antenna installations planned. Such restrictions could be found to eliminate a site at a very late stage of the process and cause much wasted effort.

E. Establish existence of line-of-sight

A clear transmission path must exist between the two link nodes of any microwave radio link. Furthermore, as the radio wave disperses as it moves away from the source, there must exist additional clearance over any obstructions to prevent attenuation of the transmitted signal. This additional clearance, known as the Fresnel zone, differs for the frequency band of the radio path, where higher frequency translates into a smaller clearance requirement.

Line of sight between two sites can be confirmed via either map-based studies or direct survey.

  • 1. A path profile is established from topographical maps which, by reference to the contours of the map, can be translated into an elevation profile of the land between the two sites in the path. Earth curvature can be added, as can know obstacles. The Fresnel Zone calculation can then be applied and an indication of any clearance problems gained.
  • 2. A path survey can be undertaken by visiting sites and observing that the path is clear of obstruction. In either event, the surveyor must allow for future obstructions that may impinge the radio path. These can be due to various causes, such as new or future buildings plans, tree or foliage growth, cranes, nearby airports and subsequent flight-path traffic, other transient traffic considerations, etc.

These are dependent upon factors such as link length, site locations, availability of topographical information and availability of tools. It is not uncommon to use both techniques for certain links. If line-of-sight cannot be achieved, this information should be processed back through the network plan and alternative path calculations and site selection performed.

F. Map package

A search map package can be prepared, the purpose of which is to provide engineering guidelines that will enable the property acquisition department to buy or lease the sites. It should contain:

  • 1. A map indicating the proposed site's general location.
  • 2. Preliminary microwave routing plan – a diagram showing how traffic from this cell site will be carried to the switch
  • 3. Future expansion – if the site is a possible future microwave hub sites, it must be so identified. Hub sites will require additional microwave antennas and mounting structures so the equipment room and power requirements must be calculated to accommodate future growth.
  • 4. Preliminary path calculations to indicate the type of: microwave equipment that will be used, such as frequency band and antenna size. This is only preliminary information and could change if the microwave routing changes.
  • 5. Tower loading specification – if a tower is proposed at the site, it must be designed for future expansion of the microwave system and possible sectorization of the site. The type of tower (self-support, guyed or monopole) selected must meet required tilt, sway and twist specifications.
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Once a potential site (building, land and tower) from the search map is identified, it must be verified by the transmission engineer and visited by a representative from various groups involved: property, civil, cellular and transmission.

The transmission group verifies line-of-sight (LOS) parameters for the microwave path. The placement of the antenna structure, equipment room and cable access-way must also be identified and photographs taken for future reference.

If LOS is not available for any other proposed site, an alternative transmission routing can be used such as an active/passive repeater or a leased-line facility. If this is not practical, then the proposed site should be rejected and a new one investigated.

Before the final design can be started, the following information in the search map package must be confirmed:

  • Microwave routing plan – is the routing valid after LOS verification?
  • Future expansion – is the site adequate to support a hub site?
  • Path calculations – is the path distance still the same? Can the frequency band be used?
  • Tower loading specification – is a higher tower required?

G. Detailed network design – frequency planning

Frequency planning is the coordination of link frequencies to minimize any interference between links within the network and those operated by other users. If a block allocation has been obtained, then planning will be the responsibility of the WLL operator, otherwise, the local regulatory authority.

Several factors must be considered that will affect the calculations of interference that will determine the optimum channel frequency for each radio link.

  • 1. Path availability target considerations, since higher availabilities will require higher levels of protection from interference and hence increase planning difficulties.
  • 2. Radiated power (EIRP)
  • 3. Link operating frequencies
  • 4. The channel plan
  • 5. The C/I performance of the equipment (how well the radio equipment can discriminate the wanted signal in the presence of interference)
  • 6. Antenna characteristics, such as radiation pattern envelope (RPE), gain and front-to-back ratio.

A new transmission diagram should be produced at least once a year, showing additional cell sites and growth.

H. Final design

This will entail a final path study, urban/rural area considerations, frequency selection, meeting with the regulators, a review of available frequency bands, frequency approval, and weather and frequency band versus path distance considerations.

A final path study must include propagation analysis and take account of reflection surfaces such as lakes, rivers, drainage and fields, sand areas, marshland and large flat roofs.

If the microwave path is in an urban area and the corresponding site can be seen with binoculars or a telescope, this is generally sufficient for LOS confirmation.

In rural areas the microwave paths are usually longer (greater than 15km) and use tower structures instead of buildings. It is difficult to verify LOS if the tower is not yet built. For these applications, the microwave path must be plotted on a map and an analysis performed to determine antenna heights taking into consideration clearance and reflection criteria.

I. Equipment/Tools used for RF and microwave survey & design:

  • GPS (Global positioning system)
  • Commercial grade compass
  • 3- Digital camera
  • 4- Binoculars
  • 5- Path loss software for microwave network designing
  • 6- Atoll software, loaded with 50m resolution digital map, for RF and microwave planning
  • 7- Spectrum analyzer, optional, to check the frequency availability/interference/over lapping.

Network Planning Survey

Wireless network planning survey is an assignment in need of painstaking efforts. Network planning survey personnel are required to plan and survey in due diligence. Network planning team is requires qualified and expert staff because of the Wireless communication is based on good planning. Interactive Euro Technologies (IET) meets all the necessary requirements needed to a good wireless communication.

Significance of the survey

The survey and design of the GSM wireless network is providing guidelines for the project to be completed at lowest costs, to meet short term and long term traffic requirements and IET has good capabilities to fulfill necessary requirements.

Contents of the survey

The survey such aspect as traffic areas distribution, wireless communication environment, project survey and other information.

Traffic Areas Distribution

  • To investigate the traffic requirements distribution within the service area, discover the location of traffic hotspots (in longitude, latitude, elevation and bearing) and subscriber population around the BTS.
  • To investigate the economic development per capital income and consumption habits.
  • To understand the communication business development plans of the carrier and make rational forecasts of the subscriber pollution growth in the period being planned. IET has qualified engineers for planning to meet all necessary requirements.

Wireless Communication Environments

To investigate the landforms, ground objects and land features in the service area. Collection of site data like longitude, latitude and elevation of the BTS/Repeater and relevant distance between two sites.

Project Survey

  • • Survey/design of the MSC, BSC, OMC and equipment room.
  • • BTS equipment room design, examination of basic BTS construction conditions (transmission, power supply, cabin and tower) as per requirements provided by the customer.

Survey Procedure

The survey falls into three stages like:

  • Survey Preparation
  • Survey Implementation
  • Survey Summarization

Technical Requirements for Survey

  • a. Follow the Criteria of Site Selection provided by the customer.
  • b. Antenna Types Criteria for sites according to the requirements of customer.
  • c. Completion of the Survey Report.

Network Planning Survey Tools

Interactive Euro Technologies (IET) Teams always equipped with following equipment & tools during RF survey: -

  • GPS
  • Compass
  • Distance Meter
  • Measuring Tape
  • Spectrum Analyzer
  • Telescope
  • Digital Camera
  • Test equipment also used
  • Vehicles

Software & Other Tools Available for RF Survey & Planning

Below mentioned equipment and tools are available with Interactive Teams to conduct RF Survey & Planning and to get the best results.

  • Digital Maps, 50/100M Resolution, (DTM+Clutter+Vector) by INFOTERRA
  • TEMS Cell Planner (TCPU)
  • Desk-cat
  • Pathloss 4.0
  • TEMS Link Planner (TLP)
  • NET-7 Planet Network Planning
  • Asset 3G
  • Agilent E6474A Network Optimization Platform
  • Agilent WALKABOUT Portable Test Tool for GSM Wireless Networks
  • RF Transceiver
  • N3970A Handheld Optical Power Meter

One Survey Team Consists of

Below mentioned equipment and tools are available with Interactive Teams to conduct RF Survey & Planning and to get the best results.

  • Digital Maps, 50/100M Resolution, (DTM+Clutter+Vector) by INFOTERRA
  • TEMS Cell Planner (TCPU)
  • Desk-cat
  • Pathloss 4.0
  • TEMS Link Planner (TLP)
  • NET-7 Planet Network Planning
  • Asset 3G
  • Agilent E6474A Network Optimization Platform
  • Agilent WALKABOUT Portable Test Tool for GSM Wireless Networks
  • RF Transceiver
  • N3970A Handheld Optical Power Meter

One Survey Team Consists of

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Survey Output Results

The output should be submitted to the customer at the end of the survey are:-

  • Survey Report for each BTS (in English)
  • BTS Equipment Room Design Drawing according to specimen provided by the customer
  • Submission of Information summary in case of new cabins and tower according to specimen provided by the customer.
  • Estimated population strength around the BTS according to specimen provided.
  • BTS Information Statement according to Specimen provided
  • Network Planning Information Requirements Statement.
  • Design Drawing for MSS, BSS and OMC Equipment Rooms according to specimen provided by the customer.

Comprehensive Survey and Options

During RF Survey and Planning, Interactive Euro Technologies (IET) presents three options for each site with 9 probabilities to avoid any disturbance and delay for the smooth planning process:

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Recently Completed Projects for RF Survey and Planning

Interactive Euro Technologies (IET) Recently Completed RF Survey & Planning of North Provinces including Balkh, Kuduz and Jowzjan of Afghanistan. We cannot provide the full sketch or mapped information because of confidentiality policy and Non Disclosure Agreement with the network owner. Below mentioned is one of the completed projects by IET

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Final Survey Report of Site Survey

Interactive Euro Technologies (IET) Recently Completed RF Survey & Planning of North Provinces including Balkh, Kuduz and Jowzjan of Afghanistan. We cannot provide the full sketch or mapped information because of confidentiality policy and Non Disclosure Agreement with the network owner. Below mentioned is one of the completed projects by IET

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Panoramic View across the site

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