Fixed Terrestial Wireless - Revision history

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2010-01-29T21:36:58Z

Reverted edits by CarmenManuel (Talk) to last version by JohnNavas

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'''This article covers the practical aspects of wireless access to the Internet via Fixed Terrestial Wireless ([http://en.wikipedia.org/wiki/radio radio]).'''

__FORCETOC__
== Introduction ==
While not widely deployed, fixed terrestrial wireless is nonetheless alive and well in some locations.

== Network Type and Infrastructure==
Fixed Terrestrial Wireless is a [[wikipedia:Point-to-multipoint|point-to-multipoint]] or '[[wikipedia:Star network|star]]' topology, much like [[Wi-Fi]], consisting of a single central hub radio (access point) with internet connectivity, and a number of fixed client radios (subscribers).
* Clients can connect to one and only one access point, and not to other clients.
* An access point can only connect to clients, not to other access points.
* Some service providers may daisy chain radio access points, if not by routing traffic from one to the next, then by daisy chaining the [[wikipedia:Backhaul (telecommunications)|backhaul]] to the Internet. This can introduce substantial [[wikipedia:Lag|latency]] for those serviced by the last radio hub on the daisy chain.

== Hardware ==

=== Access Point ===

A wireless access point (AP) is the central bridge device used in an Infrastructure wireless network. Traffic from the wireless side of the bridge is sent to the Internet side of the bridge, and vice versa. The wireless access point controls all traffic with wireless client radios. The access point is normally pole or tower mounted at a location that provides good line of sight coverage to as much of the desired service area as possible. The pole or tower will often contain two radios. One is the access point radio that the client radios communicate with. The other is a point-to-point backhaul radio that communicates back to a central office, carrying traffic between the internet [http://en.wikipedia.org/wiki/Point_of_presence pop] and the wireless access point.

=== Client Radio ===

Typically there is a radio/antenna unit mounted outside the house, in a location that has a clear view, or line of sight, to the central hub radio. The size will normally be smaller or about the same as a satellite dish. Depending on distance from the hub, the radio/antenna unit may be just a single weatherproof box, or for more distant locations, the radio/antenna may be mounted mounted on and pointed into a larger reflector that gives more gain. Unlike a satellite receiver system, the radio and the antenna are typically both located in the box mounted outside the home. The subscriber side of the radio/antenna is [http://en.wikipedia.org/wiki/Power_over_Ethernet Ethernet plus power] for the radio. Putting the radio at the antenna eliminates radio to antenna coax losses, and therefore the length of the cable run from the outside equipment indoors is not a limiting factor for signal strength. An adapter box is used inside the house to put power in the Ethernet cable to the radio, but does not feed power back towards the client side equipment.

== Coverage Area ==

=== Overview ===
Fixed Terrestrial Wireless is basically a [[wikipedia:Cellular network|cellular network]], as are [[Wi-Fi]], [[WiMAX]] and [[Cellular|cellular telephone]]. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to WiMAX, much larger than Wi-Fi, but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.

=== Link Calculations ===
For an idea of how to calculate the area covered, you need to know the specifications of the hardware at each end, and the specifics of the radio path. You can check example calculations in [[Wi-Fi#Link_Calculations]]. (Coax loss is normally zero for Fixed Terrestial Wireless since the antenna is normally attached to the radio.) However, in nearly all cases, you will be using equipment provided by the wireless service provider, and you probably won't have access to the radio specifications. The service provider will probably not make any path calculations, but will ask your location, and if it sounds possible, come out and 'take a look'. If line of sight seems OK, or even close, and the distance is OK, then they will likely just give it a try and see what they get. You should not expect your salesman or installer to be a radio engineer. You should expect the installer to be familiar with the area and know what normally will or will not work.

== Path Variables ==
=== Line of Sight ===
If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.

=== Fresnel Zone ===
The remaining issue is one of ground clearance, commonly known as [http://www.afar.net/fresnel-zone-calculator/ fresnel zone clearance], which gives you an indication of what effect ground along the path will have. If the path is very close to ground, then you probably won't have enough clearance, and will lose a few dB, but the signal should be stable.

=== Ground Reflection ===
If the path is high above ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel. It is an unfortunate fact of life that the reflectivity of the ground can change drastically. If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected. But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective. The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.

=== Rain Attenuation ===
With a radio path of less than 10 miles, the path should not normally be subject to too many variables. Rain attenuation would not normally be a problem.

==Service Speeds==

High speeds of 4.8 Mbps downlink and 1.8 Mbps uplink are quite possible. Actual speeds can vary greatly depending on provider, geography, and class (cost) of service.

JohnNavas: /* Typical */ edit

2008-12-04T18:21:41Z

Typical: edit

← Older revision		Revision as of 13:21, 4 December 2008
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	==Service Speeds==		==Service Speeds==

	~~===Typical===~~		High speeds of 4.8 Mbps downlink and 1.8 Mbps uplink are quite possible. Actual speeds can vary greatly depending on provider, geography, and class (cost) of service.
	~~Since I have not had access to any hardware manuals, and I am writing this late at night, I will just offer up so observations.~~

	~~In my area at the current time, the data rate provided by my radio link is about~~ 4.8 Mbps ~~download,~~ and ~~about~~ 1.8 Mbps ~~upload~~. ~~This~~ can ~~be controlled by the service~~ provider ~~by settings in the radio (I don't know which end) that pertain specifically to my link. This is about the same speed~~, ~~if not faster~~, ~~than I might get by a wired hookup by a cable or phone company provider. Ones upload~~ and ~~download speed to the internet can be checked at [http://www.speedtest.net/ SpeedTest]~~.

JohnNavas: /* Path Variables */ edit

2008-12-04T18:18:07Z

Path Variables: edit

← Older revision		Revision as of 13:18, 4 December 2008
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	== Path Variables ==		== Path Variables ==
	~~=== Rain Attenuation ===~~
	~~With a radio path of less than 10 miles, the path should not normally be subject to too many variables. Rain attenuation would not normally be a problem.~~

	=== Line of Sight ===		=== Line of Sight ===
	If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.		If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.
Line 47:		Line 44:
	=== Ground Reflection ===		=== Ground Reflection ===
	If the path is high above ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel. It is an unfortunate fact of life that the reflectivity of the ground can change drastically. If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected. But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective. The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.		If the path is high above ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel. It is an unfortunate fact of life that the reflectivity of the ground can change drastically. If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected. But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective. The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.

			=== Rain Attenuation ===
			With a radio path of less than 10 miles, the path should not normally be subject to too many variables. Rain attenuation would not normally be a problem.

	==Service Speeds==		==Service Speeds==

JohnNavas: /* Fresnel Zone Clearance */ edit

2008-12-04T18:17:28Z

Fresnel Zone Clearance: edit

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	If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.		If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.

	=== ~~[http://en.wikipedia.org/wiki/Fresnel_zone~~ Fresnel Zone ~~Clearance]~~ ===		=== Fresnel Zone ===
	The remaining issue is one of ground clearance, commonly known as [http://www.afar.net/fresnel-zone-calculator/ fresnel zone clearance]~~. Fresnel zone clearance~~ gives you an indication of what effect ~~the~~ ground along the path will have. If the path is very close to ~~the~~ ground, then you ~~don~~'t have ~~much~~ clearance, and will lose a few dB~~. But the path should be stable. If the path is high above the ground~~, ~~and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have~~ the ~~possibility of~~ signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel. It is an unfortunate fact of life that the reflectivity of the ground can change drastically. If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected. But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective. The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode. I suspect this is seldom done for this type of service. Maybe this whole paragraph should be ~~deleted~~.		The remaining issue is one of ground clearance, commonly known as [http://www.afar.net/fresnel-zone-calculator/ fresnel zone clearance], which gives you an indication of what effect ground along the path will have. If the path is very close to ground, then you probably won't have enough clearance, and will lose a few dB, but the signal should be stable.

	~~The only good thing to know about this fresnel zone topic~~ is that the path will ~~normally~~ be ~~short enough you don't~~ have to ~~worry about [http://en.wikipedia.org/wiki/K-factor K] changing~~ the ~~fresnel zone clearance~~.		=== Ground Reflection ===
			If the path is high above ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel. It is an unfortunate fact of life that the reflectivity of the ground can change drastically. If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected. But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective. The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.

	==Service Speeds==		==Service Speeds==

JohnNavas: /* Line of Sight */ edit

2008-12-04T18:12:40Z

Line of Sight: edit

← Older revision		Revision as of 13:12, 4 December 2008
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	=== Line of Sight ===		=== Line of Sight ===
	If you have line of sight, then ~~trees~~ or someone building and consequently obstructing the line of sight ~~WOULD be~~ a problem. If you don't have line of sight, then the path ~~may~~ still work, ~~and may~~ change with the seasons if trees are the reason for it not being line of sight.		If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.

	=== [http://en.wikipedia.org/wiki/Fresnel_zone Fresnel Zone Clearance] ===		=== [http://en.wikipedia.org/wiki/Fresnel_zone Fresnel Zone Clearance] ===

JohnNavas: /* Link Calculations */ edit

2008-12-04T18:11:00Z

Link Calculations: edit

← Older revision		Revision as of 13:11, 4 December 2008
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	=== Link Calculations ===		=== Link Calculations ===
	For an idea of how to calculate the area covered, you need to know the specifications of the hardware at each end, and the specifics of the radio path. You can check example calculations ~~for~~ Wi-Fi ~~in that section~~. However, in nearly all cases, you will be using equipment provided by the wireless service provider, and you probably won't have access to the radio specifications. ~~Note here if numbers are available.~~ The service provider will probably not make any path calculations, but will ask your location, and if it sounds possible, come out and 'take a look'. If line of sight seems OK, or even close, and the distance is OK, then they will likely just give it a try and see what they get. You should not expect your salesman or installer to be a radio engineer. You should expect the installer to be familiar with the area and know what normally will or ~~won't~~ work.		For an idea of how to calculate the area covered, you need to know the specifications of the hardware at each end, and the specifics of the radio path. You can check example calculations in [[Wi-Fi#Link_Calculations]]. (Coax loss is normally zero for Fixed Terrestial Wireless since the antenna is normally attached to the radio.) However, in nearly all cases, you will be using equipment provided by the wireless service provider, and you probably won't have access to the radio specifications. The service provider will probably not make any path calculations, but will ask your location, and if it sounds possible, come out and 'take a look'. If line of sight seems OK, or even close, and the distance is OK, then they will likely just give it a try and see what they get. You should not expect your salesman or installer to be a radio engineer. You should expect the installer to be familiar with the area and know what normally will or will not work.

	~~The above notwithstanding, here are some comments about the radio path.~~

	As in the [http://wireless.navas.us/wiki/Wi-Fi#Wi-Fi_Hardware Wi-Fi] example, it is possible to do path calculations if you know the radio specs. The calculations follow the same format. However, since the radio is normally located at the antenna, you don't have to factor in coax losses at each end. Unlike in the case if Wi-Fi (which I would expect to be an exercise in futility doing link calculations) you should be able to get numbers that approach reality. If you know the transmit power and transmit antenna gain, and you know the receiver sensitivity and antenna gain, all that is left is the fade margin and the Path Loss. Once you calculate the Path Loss, you will then be able to calculate the fade margin.

	== Path Variables ==		== Path Variables ==

JohnNavas: /* Overview */ edit

2008-12-04T15:33:26Z

Overview: edit

← Older revision		Revision as of 10:33, 4 December 2008
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	=== Overview ===		=== Overview ===
	Fixed Terrestrial Wireless is basically a [[wikipedia:Cellular network\|cellular network]], as are [[Wi-Fi]], [[WiMAX]] and [[Cellular\|cellular telephone]]. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to [[WiMAX]], much larger than [[Wi-Fi]], but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.		Fixed Terrestrial Wireless is basically a [[wikipedia:Cellular network\|cellular network]], as are [[Wi-Fi]], [[WiMAX]] and [[Cellular\|cellular telephone]]. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to WiMAX, much larger than Wi-Fi, but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.

	=== Link Calculations ===		=== Link Calculations ===

JohnNavas: /* Overview */ edit

2008-12-04T15:32:51Z

Overview: edit

← Older revision		Revision as of 10:32, 4 December 2008
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	=== Overview ===		=== Overview ===
	Fixed Terrestrial Wireless is basically a cellular ~~type configuration~~, as are Wi-Fi, WiMAX and Cellular. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to [[WiMAX]], much larger than [[Wi-Fi]], but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.		Fixed Terrestrial Wireless is basically a [[wikipedia:Cellular network\|cellular network]], as are [[Wi-Fi]], [[WiMAX]] and [[Cellular\|cellular telephone]]. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to [[WiMAX]], much larger than [[Wi-Fi]], but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.

	=== Link Calculations ===		=== Link Calculations ===

JohnNavas: /* Overview */ edit

2008-12-04T15:30:23Z

Overview: edit

← Older revision		Revision as of 10:30, 4 December 2008
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	=== Overview ===		=== Overview ===
	Fixed Terrestrial Wireless is basically a cellular type configuration, as are Wi-Fi, WiMAX and Cellular. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 miles from the hub. The coverage is ~~therefore~~ larger than ~~WiMAX~~, but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.		Fixed Terrestrial Wireless is basically a cellular type configuration, as are Wi-Fi, WiMAX and Cellular. The hub defines the 'central' point of the cell, and the distance covered will depend on antennas used, transmitter powers, receiver sensitivity, and the terrain and any interfering obstacles. This type of system can easily cover an area where subscribers are 5 or more miles from the hub. The coverage is thus similar to [[WiMAX]], much larger than [[Wi-Fi]], but limited to fixed subscriber side installations. The deployment of this system would usually be designed to cover a predetermined area of land, which may or may not be circular. Therefore, the hub may not be at the actual center of the cell, and the cell may not be circular.

	=== Link Calculations ===		=== Link Calculations ===

JohnNavas: /* Wi-Fi Hardware */ edit

2008-12-04T15:27:54Z

Wi-Fi Hardware: edit

← Older revision		Revision as of 10:27, 4 December 2008
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	* Some service providers may daisy chain radio access points, if not by routing traffic from one to the next, then by daisy chaining the [[wikipedia:Backhaul (telecommunications)\|backhaul]] to the Internet. This can introduce substantial [[wikipedia:Lag\|latency]] for those serviced by the last radio hub on the daisy chain.		* Some service providers may daisy chain radio access points, if not by routing traffic from one to the next, then by daisy chaining the [[wikipedia:Backhaul (telecommunications)\|backhaul]] to the Internet. This can introduce substantial [[wikipedia:Lag\|latency]] for those serviced by the last radio hub on the daisy chain.

	== ~~Wi-Fi~~ Hardware ==		== Hardware ==

	=== Access Point ===		=== Access Point ===

	A ~~Wireless Access Point~~ (AP) is the central bridge device used in an Infrastructure wireless network. Traffic from the wireless side of the bridge is sent to the Internet side of the bridge, and ''vice versa''. The wireless access point controls all traffic with wireless client radios. The access point is normally pole or tower mounted at a location that provides good line of ~~site~~ coverage to as much of the desired service area as possible. The pole or tower ~~mount~~ will often contain two radios. One is the access point radio~~, the one~~ that the client radios communicate with. The other is a point to point backhaul radio, that ~~goes~~ back to a central office ~~and carries the~~ traffic ~~from~~ the internet [http://en.wikipedia.org/wiki/Point_of_presence pop] to the ~~pole top~~.		A wireless access point (AP) is the central bridge device used in an Infrastructure wireless network. Traffic from the wireless side of the bridge is sent to the Internet side of the bridge, and vice versa. The wireless access point controls all traffic with wireless client radios. The access point is normally pole or tower mounted at a location that provides good line of sight coverage to as much of the desired service area as possible. The pole or tower will often contain two radios. One is the access point radio that the client radios communicate with. The other is a point-to-point backhaul radio that communicates back to a central office, carrying traffic between the internet [http://en.wikipedia.org/wiki/Point_of_presence pop] and the wireless access point.

	=== Client Radio ===		=== Client Radio ===

	Typically there is an radio/antenna unit mounted outside the house, in a location that has a clear view, or line of ~~site~~, to the central hub radio. The size will normally be smaller or about the same as a satellite dish. Depending on distance from the hub, the radio/antenna unit may be just a single weatherproof box, or for more distant locations, the radio/antenna may be mounted mounted on and pointed into a larger reflector that gives more gain. Unlike a satellite receiver system, the radio and the antenna are ~~all~~ located in the box mounted outside the home. The subscriber side of the radio/antenna is [http://en.wikipedia.org/wiki/Power_over_Ethernet ~~ethernet~~ plus power] for the radio. Putting the radio at the antenna eliminates radio to antenna coax losses, and therefore the length of the cable run from the outside equipment indoors is not a limiting factor for ~~coverage area or receive~~ signal strength. An adapter box is used inside the house to put power in the ~~ethernet~~ cable to the radio, but does not feed power back towards the client side equipment.		Typically there is a radio/antenna unit mounted outside the house, in a location that has a clear view, or line of sight, to the central hub radio. The size will normally be smaller or about the same as a satellite dish. Depending on distance from the hub, the radio/antenna unit may be just a single weatherproof box, or for more distant locations, the radio/antenna may be mounted mounted on and pointed into a larger reflector that gives more gain. Unlike a satellite receiver system, the radio and the antenna are typically both located in the box mounted outside the home. The subscriber side of the radio/antenna is [http://en.wikipedia.org/wiki/Power_over_Ethernet Ethernet plus power] for the radio. Putting the radio at the antenna eliminates radio to antenna coax losses, and therefore the length of the cable run from the outside equipment indoors is not a limiting factor for signal strength. An adapter box is used inside the house to put power in the Ethernet cable to the radio, but does not feed power back towards the client side equipment.

	== Coverage Area ==		== Coverage Area ==